1. Field of the Invention
This invention relates to electro-mechanical relays for switching high frequency signals with high reliability and stable insertion loss.
2. Description of Related Art
Many different types of switches are known for switching of radio frequency signals and other signals. Some switch types include, spring actuated contacts, electromagnetic actuators, plungers with permanent magnets, articulated joints and other movable elements. Examples of these types of switches are shown in U.S. Pat. Nos. 6,340,923, 6,337,612, 6,211,756, 6,204,740, 6,124,771, 5,894,255, 5,815,049, 5,724,014, 5,699,030, 5,652,558 and 5,499,006. Unfortunately, these switch types suffer from poor reliability, slow response time, low switch lifetime and short circuits between switch components.
Other examples of RF switches are shown in U.S. Pat. Nos. 4,298,847, 4,697,056, 4,908,588, 6,037,849 and 6,133,812. The RF switches shown in these patents use several cylindrical guide pins to guide the reed conductors in an up and down motion preventing contact between the reed conductors and the walls of the surrounding RF channels. In other words, the guide pins prevent short circuiting of the reed conductors. The electro-mechanical switches of these patents also have dielectric guide pins. The contact area between a flat surface of the conductor reed and a cylindrical surface of the dielectric guide pin has the shape of a line. These guide pins have to be precisely located in order to obtain a small clearance between the dielectric guide pins and the conductor reeds. The flat side surfaces of the conductor reeds continually interact with the cylindrical surface of the guide pins during their movement causing wear of the guide pins and shortening the life of the switch. One way to reduce wear is to increase the number of guide pins. Unfortunately, this causes the RF switch to be larger and more expensive. Additional guide pins also reduce the electrical performance of the switch.
One method to reduce wear of the guide pins is to increase the contact area between the guide pins and the conductor reeds. This method is illustrated in U.S. Pat. Nos. 5,642,086 and 5,815,057. Even with the prior art devices, a need remains for a coaxial RF switch that has a high lifetime and high reliability with precision movement.
While various RF switches have previously been used, they have suffered from unstable insertion loss, poor reliability, slow response time, low switch lifetime, short circuits and are expensive to produce.
A current unmet need exists for an improved RF switch for coaxial transmission lines that overcomes the deficiencies of the prior art.
It is a feature of the invention to provide an electro-mechanical relay for switching high frequency signals that has high reliability and low failure rates.
Another feature of the invention is to provide an electro-mechanical relay for switching high frequency signals that has stable insertion loss and is manufacturable at a low cost.
Another feature of the invention to provide an electromagnetic switching device that includes a housing having a base and a case. The case has a bore and the base has a slot. An electromagnet is mounted in the case. A reed holder has a first and second end. The first end is mounted in the bore adjacent the electromagnet. A first and second terminal are mounted in the base and extend into the slot. A guide member is mounted in the slot. An electrically conductive reed is mounted to the second end of the reed holder. The reed is supported by the guide member and extends over the terminals. The electromagnet is adapted to move the reed between a closed position in which the first and second terminals are electrically connected and an open position in which the first and second terminals are electrically disconnected. The guide member prevents rotation of the reed as it moves between the open and closed positions.